Black holes have become a topical research area over the last decade. Different numerical and analytical schemes have been setup to study the local and global dynamics of these objects, both in the astrophysical and in more abstract contexts [1]}, [2]}, [3]}, [4]}, [5]}, [6]}, [7]}, [8]}, [9]}, [10]}, [11]}, [12]}, [13]}, [14]}. The local dynamics of these objects can be tracked by the evolution of their associated horizons, the so-called dynamical horizon (and more generally, marginally trappe tubes) developed by Ashtekar and others (see the references [2]}, [3]}, [4]}). Their existence and uniqueness in some general setting was extensively dealt with in [4]} by Ashtekar and Galloway, which established constraints on the locations and occurence of dynamical horizons.
